Temperature

[jlazar]

When monitoring your MH for cold weather to avoid freezing pipes, which temperature do you key on?  Actual temperature (e.g., 36) or feels like (e.g., 28).  What effect does wind have on freezing if not directly exposed to the pipes?

 

[maverickbbd]

The pipes, tanks, etc. don't "feel" sensible or windchill effects.  But I do!  So when I feel cold I start to head south to avoid freezing pipes.  Ambient temperature is what you have to be aware of for pipes (and road conditions).

 

[Racerham]

If the pipes are not exposed, then the wind has no effect. Use the Actual Temperature to worry about freezing pipes. That is the coldest a pipe (or any other object) will get due to cooling by the air.

The "feels Like" temperature describes how fast an object cools, or how much heat must be generated to maintain a given temperature. ie. a heated object (like skin) looses heat as fast as if the temperature were the "feels like" temperature with no air movement.

If you have a heating tape on a pipe that is exposed to wind, then the heating tape must have enough heat generation capacity to keep the pipe warm at the "feels like" temperature, but if it is not exposed to wind, the heat tape only has to have enough capacity to keep the pipe warm to the Actual temperature.

HTH

Mike

 

[Gary RV_Wizard]

Great explanation, Mike.

 

[therealsimpsons]

Hmmm, I'm thinking an inanimate object could never be colder than the air temperature. Yes or no? "Feels like" only applies to living organisms.

I used to hear truckers parking in a truck stop say on a CB radio that they had to face away from the wind because the wind chill factor would be worse and perhaps freeze their coolant. I used to think that was horse pucky, but maybe not?

Stan

 

[Lowell]

Hmmm, I'm thinking an inanimate object could never be colder than the air temperature

I agree with the above statement.  If an inanimate object , such as a thermometer got colder than the actural temperature, how would you know what was the actual temperature? 

A way to tell would be to get two thermometers that read the same and put one out in the wind and the other in a area outside protected from the wind and see if there is any difference.

 

[carson]

Good point to debate.  Probably lot's of theories will prevail. Perhaps the link below will help solve the curiosity. A lot of entries on search engines.

>>>  http://www.uu.edu/dept/physics/scienceguys/2002feb.cfm

 

[jlazar]

Great explanations.  Thanks Mike and Carson.

 

[Gary RV_Wizard]

"wind chill" is a complex phenomena, as Racewrham (Mike) explained. It actually does cause a surface to lose heat rapidly and it can indeed cause it to drop below the ambient temperature. But then heat begins to flow back into the relatively cold surface from the surrounding air and from the rest of the object, so the surface temp stabilizes somewhere in between. The surface and ambient temps may not exactly match until the wind dies. The heat content of an object, even something as big as an RV, is not a stable thing unless it "soaks" for 24 or more hours with no other heat inputs, whether internal (e.g. a furnace) or external.

 

[bucks2]

When people explain to me that the wind doesn't actually take heat away from inanimate objects, I always ask if they blow on hot soup?

Ken

 

[Larry N.]

The wind chills moist things more rapidly than dry things, generally speaking, I suspect because the moisture makes it a bit like a swamp cooler.

 

[driftless shifter]

Wind chill definitley affects machinery, whether a physical plant or just an engine. The temp may not drop below the actual outdoor temp, but whatever heat there is will be sucked out faster when windy compared to a still day. Why do so many semi trucks block off the front grill for the winter. Why did we have "storm" windows or shutters on homes before thermo-pane windows. Lets not even bring up drafts creeping in and sucking even more heat. Heat ALWAYS flows toward cold, It's never the other way around. The heat flows to the outside surfaces and is rapidly dissipated. Virtually anything warmer than actual outdoor temperature "feels" windchill, as any heat is sucked away faster by cold wind than by cold still air.

 

[John From Detroit]

Heat is lost from a body or any LIQUID by three means

Conduction, radiation and evaporation.

Radiation is not affected by the movement of air.

Air, however, is a very poor conductor of heat, this is why "Foam cell" insulation works so well.  But it can absorb a bit of heat, so if we move more fresh cold air in to replace the now hot air, it an absorbe a bit more heat. So yes, moving air does cool even a block of steel faster than air that is not moving.

And evaporation.. As the air close to the hot liquid or body becomes saturated with moisture (The evaporation of which takes great hugh gobs of heat from the body, or the hot bowl of soup) fresh dry air comes in to replace it and evaporation continues.

By the way this is the real reason you blow on your soup.

 

[driftless shifter]

Radiation is affected by moving air. The moving air is replenished with fresh unwarmed air. Aircooled engines wouldn't need fans or forward motion for cooling. In MA. aircooled motorcycles are allowed cautious lane splitting and breakdown lanes during a traffic jam for this explicit reason.

 

[carson]

Wow, I have never given that a thought. Guess because I have never owned a bike.

Sure makes sense to me. Do bikes have an over-temperature warning system ?

 

[captsteve]

Sure Carson, The older ones would stop running when the piston fuzes to the cylinder wall, A good indication that it's hot out! he he he ! Then came a temp gauge on some.